Related papers: Transversity and Collins Functions: from e+ e- -->…
We perform a comprehensive study within quantum chromodynamics (QCD) of dihadron observables in electron-positron annihilation, semi-inclusive deep-inelastic scattering, and proton-proton collisions, including recent cross section data from…
In the fragmentation of a transversely polarized quark several left-right asymmetries are possible for the hadrons in the jet. When only one unpolarized hadron is selected, it exhibits an azimuthal modulation known as Collins effect. When a…
Predictions for the transverse single spin asymmetry (SSA), A_N, are given for the inclusive processes l p(transv. pol.) --> h X and l p(transv. pol.) --> jet + X, which could be measured in operating or future experiments. These estimates…
HERMES has measured azimuthal single-spin asymmetries of pions and charged kaons produced in deep-inelastic scattering of electrons and positrons off a transversely polarized hydrogen target. These asymmetries provide information about the…
COMPASS is a fixed-target high energy physics experiment at the SPS at CERN \cite{Abbon:2007pq}. One of the important objectives of the experiment is the exploration of the transverse spin structure of the nucleon via spin dependent…
We discuss transverse polarization distribution and fragmentation functions, in particular, T-odd functions with transverse momentum dependence, which might be relevant for the description of single transverse spin asymmetries. The role of…
This work reports the first observation of azimuthal asymmetries around the thrust axis in $e^+e^-$ annihilation of pairs of back-to-back charged pions in one hemisphere, and $\pi^0$ and $\eta$ mesons in the opposite hemisphere. These…
Measuring single spin asymmetries in semi-inclusive deep-inelastic scattering (SIDIS) on a transversely polarized target gives a handle to investigate the transversity distribution and transverse momentum dependent distribution functions.…
The $T$-odd distribution functions contributing to transversity properties of the nucleon and their role in fueling nontrivial contributions to azimuthal asymmetries in semi-inclusive deep inelastic scattering are investigated. We use a…
By considering semi-inclusive deep-inelastic scattering and the (complementary) $q_T$-spectrum for Drell-Yan lepton pair production we derive the QCD evolution for all the leading-twist transverse momentum dependent distribution and…
Single-spin asymmetries in semi-inclusive pion production are measured by the HERMES experiment for the first time, with a transversely polarised hydrogen target. Two different sine-dependencies are extracted which can be related to the…
We study the beam single spin asymmetry in semi-inclusive hadron production in deep inelastic scattering in at order 1/Q. There are two competing contributions: the leading order transverse momentum dependent parton distribution…
We present measurements of Collins asymmetries in the inclusive process $e^+e^- \rightarrow h_1 h_2 X$, $h_1h_2=KK,\, K\pi,\, \pi\pi$, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb$^{-1}$ collected by the BaBar…
The NJL-jet model is extended to accommodate hadronization of a transversely polarized quark in order to explore the Collins effect within a multihadron emission framework. This is accomplished by calculating the polarized quark spin flip…
We present a phenomenological extraction of transversity distribution functions and Collins fragmentation functions by simultaneously fitting to semi-inclusive deep inelastic scattering and electron-positron annihilation data. The analysis…
The most recent data on the weighted transverse single spin asymmetry A_{UT}^{\sin(\phi_h-\phi_S)} from HERMES and COMPASS collaborations are analysed within LO parton model; all transverse motions are taken into account. Extraction of the…
In the TMD approach, the average transverse momentum of the unpolarised TMD PDFs and FFs is crucial not only to reproduce unpolarised cross sections and hadron multiplicities, but also for the understanding of azimuthal and spin…
We discuss the properties of fragmentation functions arising from the interference of two leading hadrons produced inside the same jet in the current fragmentation region of a hard process. For the case of semi-inclusive Deep Inelastic…
We present a phenomenological analysis of the $\cos 2 \phi$ asymmetry recently measured by the COMPASS and HERMES collaborations in unpolarized semi-inclusive deep inelastic scattering. In the kinematical regimes explored by these…
High precision measurements of the polarized electron beam-spin asymmetry in semi-inclusive deep inelastic scattering (SIDIS) from the proton have been performed using a 10.6~GeV incident electron beam and the CLAS12 spectrometer at…